This invention relates to a brake booster having a two-way valve which consists of a valve seat mounted on a housing, of a valve body slideable by means of an actuating rod, and of a closing member loaded by spring forces against the valve body, and wherein the closing member is movable onto the valve seat by displacement of the actuating rod, whereupon the valve body is movable away from the closing member.
Such a brake booster is known from the German Pat. No. 1,228,931.
In this known brake booster, the function of the two-way valve is to first interrupt a vacuum connection between two work chambers of the brake booster when displacing the actuating rod, and then second to permit atmospheric pressure to enter into one of the two work chambers that provides the booster action. The disadvantage of this known brake booster lies in that brake application requires considerable lost travel of the brake pedal. This leads to a poor response and/or release behaviour and, consequently, to a large hysteresis of the brake system.